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Abstract

Direct conversion of nuclear energy to electricity has been a challenging problem since the
inception of the generation of electricity from nuclear reactions. The development of wide bandgap,
p-n junctions in materials such as diamond, gallium nitride, aluminum nitride, and silicon
carbide is at the heart of this research. A p-n junction in materials with band-gaps greater than 3
eV can be used in nuclear energy conversion in multiple ways. For example, for direct
conversion of the kinetic energy of particles from the decay of radioisotopes, a diamond p-n
junction has some unique advantages. It is less susceptible to radiation damage than SiC, GaN,
and AlN because, at high temperatures, it can self-anneal point defects caused by radiation
damage. A method which eliminates the radiation damage problem is a Two-Step Photon
Intermediate Direct Energy Conversion (PIDEC) method that uses the efficient generation of
photons from the interaction of particulate radiation with fluorescer media. The photons are then
transported to wide band-gap photovoltaic cells where electrical current is generated. PIDEC
holds the promise of 40% energy conversion efficiency in a single cycle. PIDEC can be applied
both to large power generation systems and to small scale nuclear batteries based on
radioisotopes (Radioisotope Energy Conversion System-RECS). Students and faculty have built
a test stand for the PIDEC and RECS concepts which tests the physics of fluorescence
production from the interaction of radiation with various fluorescer media, the transport of
photons, radiation shielding methods, photovoltaic conversion with wide band-gap photovoltaic
cells, and conversion efficiencies. The technology is licensed to a Missouri company (US
Semiconductor, Independence MO) and is helping to facilitate economic development in the
State of Missouri.